The present invention pertains to a method and device for managing primary functions and addressing in computers containing integrated circuits and similar electrical devices. More specifically, a method and device are provided for maintaining the performance of primary functions for a group of electrical devices even when a primary electrical device is disabled.
Primary functions for a group of electrical devices in a computer system are certain functions that are only performed by one of the group of electrical devices. For example, the provision of a clock signal may be a primary function because the group of electrical devices is synchronized through a single clock signal.
A codec (coder/decoder) is an integrated circuit or other electronic circuitry combining the circuits needed to convert digital signals into analog signals and to convert analog signals into digital signals. Audio frequency codecs are used in computers, for example, on modem (modulator/demodulator) and sound cards to convert digital signals that can be read and stored by the computer into analog signals that can be transmitted over telephone wires or output to speakers for sound. Codecs on these devices also convert incoming signals from telephone wires or input sound signals, into a digital format that can be read, understood, and stored by the computer.
Traditionally, audio and modem hardware has been provided on separate boards that plug into a computer motherboard via industry standard expansion slots, for example, peripheral component interconnect (PCI) input/output expansion slots. See PCI Specification, Rev. 2.2 (1998) (“PCI Specification”), PCI Special Interest Group, Hillsboro, Oreg. Examples of these include modem cards and sound cards. Advantages in computer system design and production can be gained by providing audio and modem hardware on the computer system motherboard itself. The desktop system manufacturer can implement audio and/or modem solutions on the motherboard at lower cost and thereby make standard expansion slots in the system available for other additional plug-in peripherals. This design is described by the Audio Codec '97 Specification, Version 2.1 (“AC '97 Specification”), published by Intel Corporation, Santa Clara, Calif.
A disadvantage of providing all the hardware of, for example, a modem on the motherboard is that the entire motherboard design approval and production process may be delayed pending approval of the modem hardware design by the Federal Communications Commission (FCC) and other worldwide telecommunications certifying agencies. This delay could significantly impact a computer manufacturer in the time-sensitive computer market. Furthermore, the modem attach rate in some cases does not warrant placing all the modem architecture “down” on the motherboard. Since there are multiple options for hardware manufacturers to place codecs in different locations, a flexible system is required for addressing codecs and routing codec signals to various components of the computer system. Various systems exist for identifying, initializing, and controlling various components that may be installed in computer systems. For example, computer systems employing so-called “plug-and-play” technology automatically detect when a new component has been plugged into the computer system. The plug-and-play components store information about their nature and resource requirements in their local non-volatile memories. System software and/or firmware reads the memory entries to determine the type of component and its characteristics, and can reconfigure software programs, including the operating system, to enable use of the new component. See PCI Specification. Systems such as these can be used to eliminate the need for a user to set switches or jumpers or to perform other difficult system configuration tasks.
An example of the use of a digital signal to auto detect the presence or absence of a hardware component is a presence detect signal for a memory chip (e.g., a dynamic random access memory (DRAM) dual in-line memory module (DIMM)). A presence detect signal is a means of identifying a memory chip to the memory controller logic of a computer system, using a pin on the memory chip to indicate presence detect information. For example, the Serial Presence Detect (SPD) scheme uses a serial EEPROM (electrically erasable, programmable, read-only memory) to store the presence detect information for a DRAM DIMM and requires only two pins (one for clocking it and one for data). Presence pins and their associated EEPROM, located on a DIMM module, indicate the presence or absence of the DIMM to the system motherboard. An example of a BIOS-controlled signal used to operate on components of a computer system is the use of a signal to mute a computer audio system, upon receiving an input from a user.
In addition to auto-detecting and assigning addresses to electrical devices on installation, these functions may also be required when an electrical device is disabled. This may occur, for example, when a new component is installed in an environment in which only a limited number of electrical devices may operate, or to free up resources.